echo 1111111 > z.txt
exec {newFD}< <(tail -f -c +0 "z.txt")

while IFS= read -r LINE0 <&${newFD}
do
    printf '%s' "$LINE0"
done

echo 1111111 > z.txt
while IFS= read -r LINE0 <&${newFD}
do
    printf '%s' "$LINE0"
done {newFD}< <(tail -f -c +0 "z.txt")